The present invention relates to coated abrasive articles and to methods of making and using the same.
In general, coated abrasive articles have abrasive particles secured to a backing. More typically, coated abrasive articles comprise a backing having two major opposed surfaces and an abrasive layer secured to a major surface. The abrasive layer is typically comprised of abrasive particles and a binder, wherein the binder serves to secure the abrasive particles to the backing.
One common type of coated abrasive article has an abrasive layer which comprises a make layer, a size layer, and abrasive particles. In making such a coated abrasive article, a make layer comprising a first binder precursor is applied to a major surface of the backing. Abrasive particles are then at least partially embedded into the make layer (e.g., by electrostatic coating), and the first binder precursor is cured (i.e., crosslinked) to secure the particles to the make layer. A size layer comprising a second binder precursor is then applied over the make layer and abrasive particles, followed by curing of the binder precursors.
Another common type of coated abrasive article comprises an abrasive layer secured to a major surface of a backing, wherein the abrasive layer is provided by applying a slurry comprised of binder precursor and abrasive particles onto a major surface of a backing, and then curing the binder precursor.
Optionally, coated abrasive articles may further comprise, for example, a backsize layer (i.e., a coating on the major surface of the backing opposite the major surface having the abrasive layer), a presize layer (i.e., a coating between the abrasive layer and the major surface to which the abrasive layer is secured), and/or a saturant which coats both major surfaces of the backing. In another aspect, coated abrasive articles may further comprise a supersize layer covering the abrasive layer. The supersize layer typically includes grinding aids and/or anti-loading materials.
Typically, binder precursors employed in make, size, and/or slurry layers of the abrasive layer are cured at an elevated temperature (e.g., in the range of 100 to 170xc2x0 C.) for a length of time (e.g., in the range of from 15 minutes to 8 hours). Under such conditions, many thermally-sensitive materials that would otherwise be useful as backings in abrasive articles may soften, warp, decompose, etc. It would be desirable to have useful make, size, and/or slurry layer formulations that can be cured at relatively low temperatures, thereby increasing the number of materials that are suitable for use as backings.
Further, after curing the abrasive layer at the elevated temperature, the backing and the abrasive layer typically shrink on cooling. The backing and abrasive layer usually have different coefficients of thermal expansion. As a result, differential shrinkage and/or expansion of the backing and abrasive layer normally occurs. For relatively flexible backings, this differential shrinkage usually causes the finished article to curl. The amount of curl depends on, for example, among other factors, the magnitude of the difference between the various coefficients of thermal expansion of the backing and the abrasive layer. In the case of polypropylene backings, this problem may be especially noticeable. Generally, this effect is proportional to difference between the curing temperature and ambient temperature. Excessive curl may cause problems in handling and/or using the coated abrasive article. By way of illustration, FIG. 1 is a photograph of a prior art coated abrasive article (prepared according to Comparative Example 1) having excessive curl, which was cured at elevated temperature. Thus, it would be desirable to provide coated abrasive articles that do not have excessive curl, and methods for making such articles.
In cases in which curling of the coated abrasive article does not occur, such as in the case of a rigid backing, differential shrinkage may result in an accumulation of stress at, for example, the interface between the backing and the make layer (and/or between the make and size layers). Such accumulated stress at the interface may lead, for example, to less than desirable adhesion at the interface. It would be desirable to reduce the level of such interfacial accumulated stress.
Simply reducing the temperature used to cure binder precursors in make, size, and/or slurry layers may result in a reduced degree of cure, which may not be sufficient to provide the desired, or even useful, durability and/or cut performance of the coated abrasive article.
It would be desirable to have materials and processes for making coated abrasive articles that have low levels of interfacial accumulated stress and/or reduced curl, yet that achieve a degree of cure sufficient to provide a coated abrasive article having at least good abrasive performance.
The present invention provides a solution to problems of interfacial stress and/or curl in coated abrasive articles by utilizing a binder precursor comprising a mixture of acrylate and epoxy functional materials.
In one aspect, the present invention provides a coated abrasive article comprising:
a backing having a major surface; and
an abrasive layer secured to at least a portion of the major surface, the abrasive layer comprising a binder and abrasive particles, wherein the binder comprises a reaction product of components comprising polyfunctional acrylate, alicyclic polyepoxide, and aromatic polyepoxide having an average epoxy functionality of at least 2.5.
In another aspect, the present invention provides a coated abrasive article comprising:
a backing having a major surface;
an abrasive layer secured to at least a portion of the major surface, the abrasive layer comprising:
a make layer comprising a first binder;
abrasive particles at least partially embedded in the make layer; and
a size layer comprising a second binder, at least partially covering the abrasive layer,
wherein at least one of the first or second binders comprise a reaction product of components comprising polyfunctional acrylate, alicyclic polyepoxide, and aromatic polyepoxide having an average epoxy functionality of at least 2.5.
In another aspect, the present invention provides a coated abrasive article comprising:
a backing having a major surface;
an abrasive layer secured to at least a portion of the major surface, the abrasive layer comprising a slurry layer comprising a binder and abrasive particles, wherein the binder comprises a reaction product of components comprising polyfunctional acrylate, alicyclic polyepoxide, and aromatic polyepoxide having an epoxy functionality of at least 2.5.
In another aspect, the present invention provides a method for making a coated abrasive article comprising:
providing a backing having a major surface;
applying a make layer comprising a first binder precursor onto at least a portion of the major surface of the backing;
at least partially embedding a plurality of abrasive particles into the make layer;
curing the first binder precursor;
applying a size layer comprising a second binder precursor onto at least a portion of the make layer and plurality of abrasive particles; and
curing the second binder precursor to provide a coated abrasive article, wherein at least one of the first or second binder precursors comprises polyfunctional acrylate, alicyclic polyepoxide, and aromatic polyepoxide having an average epoxy functionality of at least 2.5, and wherein at least one of the first or second binder precursors is cured by exposure to actinic radiation.
In another aspect, the present invention provides a method for making a coated abrasive article comprising:
providing a backing having a major surface;
applying a slurry comprising a binder precursor and abrasive particles onto at least a portion of the major surface of the backing, the binder precursor comprising at least one polyfunctional acrylate, at least one alicyclic polyepoxide, and at least one aromatic polyepoxide having an epoxy functionality of at least 2.5; and
curing the binder precursor by exposure to actinic radiation to provide a coated abrasive article.
In another aspect, the invention provides a method of abrading a workpiece comprising:
providing a coated abrasive article comprising:
a backing having a major surface;
an abrasive layer secured to at least a portion of the major surface, the abrasive layer comprising a make layer comprising a first binder and abrasive particles; and
a size layer comprising a second binder at least partially covering the abrasive layer, wherein at least one of the first or second binders comprise a reaction product of components comprising at least one polyfunctional acrylate, at least one alicyclic polyepoxide, and at least one aromatic polyepoxide having an average epoxy functionality of at least 2.5;
frictionally contacting at least a portion of the abrasive layer with at least a portion of the surface of the workpiece; and
moving at least one of the coated abrasive article or the workpiece relative to the other to abrade at least a portion of the surface.
In another aspect, the invention provides a method of abrading a workpiece comprising:
providing a coated abrasive article comprising:
a backing having a major surface;
an abrasive layer secured to at least a portion of the major surface, the abrasive layer comprising a slurry layer comprising a binder and abrasive particles,
wherein the binder comprises a reaction product of components comprising
at least one polyfunctional acrylate, at least one alicyclic polyepoxide, and
at least one aromatic polyepoxide having an average epoxy functionality of at least 2.5;
frictionally contacting at least a portion of the abrasive layer with at least a portion of the surface of the workpiece; and
moving at least one of the coated abrasive article or the workpiece relative to the other to abrade at least a portion of the surface.
Coated abrasive articles prepared according to the present invention may be cured at temperatures below about 100xc2x0 C., resulting in a relatively low degree of curl, while achieving at least good levels of abrading performance.
As used herein:
xe2x80x9cacrylatexe2x80x9d includes both acrylate and methacrylate;
xe2x80x9cacrylate functionalityxe2x80x9d refers to the number of acryloxy groups per molecule;
xe2x80x9cacryloxyxe2x80x9d includes both acryloxy and methacryloxy;
xe2x80x9cactinic radiationxe2x80x9d means particulate and non-particulate radiation and includes electron beam radiation as well as electromagnetic radiation having at least one wavelength in the range of from about 200 to about 700 nanometers;
xe2x80x9calicyclicxe2x80x9d means aliphatic and containing at least one saturated cyclic ring;
xe2x80x9calicyclic polyepoxidexe2x80x9d refers to an alicyclic material having an average epoxy functionality of at least 2;
xe2x80x9caromaticxe2x80x9d means containing at least one aromatic ring;
xe2x80x9caverage acrylate functionalityxe2x80x9d refers to the average number of acryloxy groups per molecule; it is determined for a specified material by dividing the total number of acryloxy groups by the total number of molecules having acryloxy groups;
xe2x80x9caverage epoxy functionalityxe2x80x9d refers to the average number of epoxy groups per molecule; it is determined for a specified material by dividing the total number of epoxy groups by the total number of molecules having epoxy groups;
xe2x80x9cbireactive compoundsxe2x80x9d are those which contain at least one ethylenically-unsaturated group and at least one 1,2-epoxide group;
xe2x80x9ccrosslinkedxe2x80x9d means having polymeric sections that are interconnected through chemical bonds (i.e., interchain links) to form a three-dimensional molecular network;
xe2x80x9cepoxy functionalityxe2x80x9d refers to the number of epoxy groups per molecule;
xe2x80x9cepoxy resinxe2x80x9d refers to a material containing molecules having at least one epoxy group;
xe2x80x9cepoxy groupxe2x80x9d refers to an oxiranyl group;
xe2x80x9coligomerxe2x80x9d refers to a polymer molecule having 2 to 10 repeating units (e.g., dimer, trimer, tetramer, and so forth) having an inherent capability of forming chemical bonds with the same or other oligomers in such manner that longer polymeric chains can be formed therefrom;
xe2x80x9cphotoinitiatorxe2x80x9d refers to a substance, which, if exposed to electromagnetic radiation having at least one wavelength in the range of from about 200 to about 700 nanometers, forms an initiator for free-radical polymerization;
xe2x80x9cphotocatalystxe2x80x9d refers to a substance, which, if exposed to electromagnetic radiation having at least one wavelength in the range of from about 200 to about 700 nanometers, forms a catalyst for cationic polymerization; and
xe2x80x9cpolyfunctional acrylatexe2x80x9d refers to a material having an average acrylate functionality of at least 2.